For smooth entry of canal water, the angle between canal head regulator and weir/barrage is generally kept:

Explanation:

A head regulator is generally aligned at an angle of 90^∘ to 110^∘ to the axis of the barrage in order to minimize the entry of sediment entering into the channel, besides preventing backflow and stagnant pools in the under-sluice pocket that lies in the vicinity of the regulator. Steel gates of spans usually in the range of 6 to 8 m, for manual operation, are provided in the regulator to control the discharge. Larger spans can be adopted for gates that are operated by electric winches.

Hence option (2) is the correct answer.